Undifferentiated carcinoma of the pancreas: analysis of intermediate filament profile and Ki-ras mutations provides evidence of a ductal origin.

Undifferentiated carcinomas and osteoclast-like giant cell tumours of the pancreas commonly contain foci of neoplastic ductal glands. To test the hypothesis that undifferentiated carcinomas and osteoclast-like giant cell tumours have a ductal origin, the immunocytochemical cytokeratin pattern and the frequency and type of Ki-ras mutations at colon 12 were studied in a series of 17 undifferentiated carcinomas and two osteoclast-like giant cell tumours. The cytokeratin features of undifferentiated carcinomas and osteoclast-like giant cell tumours were compared with those found in 10 ductal adenocarcinomas, 20 acinar cell carcinomas, 25 neuroendocrine tumours, and 15 solid-pseudopapillary tumours. All undifferentiated carcinomas and osteoclast-like giant cell tumours stained with at least one cytokeratin antibody, and 13/19 of them with antibodies against cytokeratins 7, 8, 18, and 19. The latter cytokeratins were expressed in all ductal adenocarcinomas, but only in 15/20 acinar cell carcinomas, 2/25 neuroendocrine tumours, and 1/15 solid-pseudopapillary tumours. In addition to cytokeratin, 15/19 undifferentiated carcinomas/osteoclast-like giant cell tumours were positive for vimentin. Ki-ras mutations at codon 12 were found in 10 undifferentiated carcinomas and one osteoclast-like giant cell tumour from which DNA could be successfully amplified. The Ki-ras mutation patterns were analysed in six tumours and corresponded to those typical of ductal adenocarcinomas. In tumours with ductal and anaplastic components, both components revealed identical mutation patterns. From these findings, it is concluded that both undifferentiated carcinomas and osteoclast-like giant cell tumours belong to the pancreatic tumours that show a ductal phenotype. Since undifferentiated carcinomas and osteoclast-like giant cell tumours share the same cytokeratin and Ki-ras features, they are probably derived from the same cell lineage.